They have never worked for me, with one exception that works flawlessly: mplayer on the command line.

Terminal -> root -> apt-get install mplayer

After you're done installing choose either to rename the sub-file (if necessary) to the same name as the movie and simply start the movie with:
mplayer name_of_the_movie

else:

mplayer name_of_the_subs name_of_the_movie